In long endless conveyor belts of the type having an electrically insulating body used to convey bulk material, there is a possibility of encountering a rip in the belt. This may occur, for example, by sharp objects being dropped thereon at a loading station. It is desirable to promptly detect such longitudinal rips and, preferably, shut down and repair the conveyor belt upon such detection, thereby minimizing damage to the belt.
In prior art structures as described, for example, in U.S. Pat. No. 3,792,459 issued to Frank D. Snyder, there is disclosed a conveyor belt rip detector system of the type in which the instant invention may be employed. In such a rip detector system, a plurality of equally spaced antenna are imbedded transversely at spaced-apart locations in the belt so as to periodically couple an electrical signal from a transmitter probe to a receiver probe while the belt, with its respective antennae, moves past the electrical sensor probes. The detected electrical signals may thus function to monitor the performance of the belt and shut down the system in response to a break in an antenna which would be indicative of a longitudinal rip in the belt. Detection of the break will permit correction before the break or rip gets too long and seriously destroys the entirety of the belt or before the belt assembly ceases to function properly. A failure, noted timely, can be corrected with minimum cost and inconvenience.
In the prior art devices it has been the general practice to utilize antennae made of metallic screens or wires such as steel extending transversely across the width of the belt, at equally spaced apart distances. Such wires function properly during normal operations for a period of time. Unfortunately, however, due to movement of the belt and wires around the conveyor rollers of the system, continued flexing stresses upon the antenna wires may cause premature breakage of the wires, thus causing a malfunction in the system. Metallic wires are also susceptible of breakage caused by ore dropped on the belt at a loading station. A broken antenna, caused by failure of any nature, will undesirably give the appearance to the control system that there is a rip in the belt. The system could then improperly shut down the conveying system when in fact there is no such rip in the belt. Alternate programming of the control system may also be employed.